SOME PEOPLE are fanatic about jogging, others about swimming or yoga. Although similarly in the service of physical fitness and peace of mind, my fanaticism is of a different sort. Armed with baking soda, hydrogen peroxide, strong salt water, an electric toothbrush, a Water Pik, a plastic toothpick holder and the round toothpicks to go with it, I have become a ritual slave to oral hygiene.

To begin at the beginning would probably take me back to my teenage years. It is typically then -- so experts say -- that the bacteria that cause severe periodontal disease ("pyorrhea") start to burrow into the gums. Their encounters with white blood cells there produce a chemical reaction that slowly, but inexorably, attacks the teeth and the underlying bone and connective tissue holding them in place. However, my troubles began in earnest only a year or so ago when I could no longer ignore a frequent sour taste in my mouth and rivulets of blood whenever I brushed my teeth or bit into something hard.

At that, I was probably lucky. I was well into my 40s by that time and was to lose just one tooth. It is at about age 30 that periodontal disease, which 9 out of 10 adults have to at least some degree, becomes the cause of more tooth loss than all other causes combined. Most of the millions of people who wear dentures have been driven to them by exactly this.

Frequent visits to my dentist, where his hygienist periodically scaled or curetted my gums to remove the corallike plaque that had accumulated from germ life, and conscientious brushing and flossing on my part, soon ended my constant worry about bad breath and made my gums both less swollen and less prone to bleed. However, I had seen a periodontist before embarking on this crash program and, after painstakingly going over my mouth and taking extensive X-rays, he had presented me with some very bad news.

Using an instrument called a periodontal probe, he had found that deep pockets had formed near almost every tooth. In these enlarged spaces at the gum margins, the toxins of chronic infection had already undermined the support of several teeth.

Extensive surgery was advised to remove or shave down these pockets so that I could do a more effective job of home care. I was told to have one already wobbly tooth extracted, to get my gums and the rest of my teeth into the best shape possible, and to return for the surgery in about a year. It would take six months to complete and would cost $2,500 or more, depending on the state of my mouth at the time. Stealing a peek at the periodontist's treatment plan when he sent it to my regular dentist, I noted that the prognosis was "fair to good."

THERE MATTERS might have rested had I not done some reading suggesting that there is no conclusive evidence that people who have gum surgery, even repeatedly, keep their teeth any longer than people who do not. From a call to the National Institute of Dental Research (a part of the National Institutes of Health), I learned of an experimental alternative program there and, after obtaining a referral from a physician friend, became a patient of the NIDR's Dr. Paul H. Keyes.

Keyes is perhaps best known in dental circles for animal experiments he performed with Dr. Robert Fitzgerald demonstrating conclusively what had long been suspected but never proved: that bacteria cause tooth decay. He also deals with periodontal disease as fundamentally a problem of infection. For this reason his office is equipped with a $2,000 instrument few other dental offices have -- a microscope linked to a camera and small television screen that fit neatly on a countertop.

As he took sample scrapings from my mouth and displayed them for me on the screen, hundreds of thousands of rod-shaped and corkscrew-shaped bacteria danced before my eyes like nothing so much as a blazing brushfire, while more slowly moving pus cells ominously reminded me that pyorrhea means "discharge of pus." With the microscope Keyes cn tell at once -- and so can the patient -- whether the scaling he does and the self-care he prescribes are having the desired effect of extinguishing these fires. Without it, both patient and dentist would be in the dark.

Keyes showed me how to wet baking soda with just enough hydrogen peroxide to make it into a paste and how to massage it into my gums first with a toothpick placed in a special holder (or with a rubber tip) and then with an electric toothbrush. I was to do this once a day on both sides of my gums.

For many patients this, followed by use of a Water Pik, empties the germs from those bacterial pockets for as long as the patient sticks to the routine, or at least reduces the germs to the point where the destruction does not progress. Keyes chose baking soda and hydrogen peroxide for the job not only because they are harmless and inexpensive, but also because baking soda shrivels the germs and hydrogen peroxide introduces oxygen into the mouth. The more oxygen there is in their environment, the less likely these bacteria are to survive.

More often than not, the payoff from this treatment is gratifyingly fast. Generally, it is only a few weeks before bad breath disappears, gums no longer bleed when probed, and loose teeth begin to tighten up. However, the microscope may disclose persistent underlying infection, and this calls for the introduction of a strong table salt solution -- epsom salts if the patient has high blood pressure and must avoid sodium -- into the Water Pik.

The Water Pik must be flushed out after each use to avoid damage to its internal parts. Also, some people find that the salt sclution stings a little at first. But, besides being germicidal, it tends to shrink the gums, partially accomplishing chemically what the periodontist does with the knife. The result is that it becomes easier to get the baking soda disinfectant paste into the pockets, making the minor inconveniences of the routine worthwhile.

When the microscope continues to disclose a germ population that is down but not out, Keyes has one more weapon in his arsenal: an antibiotic tablet (tetracycline) between meals and at bedtime for two weeks. Ironically, a patinent may find it harder to remember to take the pills at the proper intervals than to practice the more complicated rites involving soda, salt, toothpicks and Water Pik. Tetracycline should not be taken within an hour of having anything to eat, or during the last half of pregnancy, because it may permanently discolor all of an infant's teeth.

OF THE 75 or so people with severe gum disease treated by the NIDR in the last three years, some had sought to avoid surgery and others had had it at least once, only to have it fail. Most whose mouths were not already in hopeless condition have retained all or nearly all their teeth.

Much the same has been true of the patients of the few other dentists who have invested in a microscope like Keyes' and tried his techniques. One of these continues to do gum surgery, but much more sparingly than before. His billing for such surgery dropped from $30,000 in 1974 to just $800 last year, and even those patients on whom he operates are taught the NIDR regimen.

However, just as gum surgery is actually not a cure for periodontal disease, neither is the Keyes method, which works only for as long as the patient practices it religiously and which may eventually lose its effectiveness anyway. Not enough patients have used it long enough to tell.

Nor will salt and baking soda have the desired effect if the patient uses them but fails to get them where they need to go, as sometimes happens. Neither will they or tetracycline repair damage already done. Their purpose is to keep periodontal disease from getting worse. And it must be said that no study comparing their effectiveness with that of gum surgery has been performed.

Still, only about 2,500 of the nation's dentists have had the advanced training in gum surgery that qualifies them as periodontists, whereas an estimated 32 million Americans have pyorrhea so severe that they are in imminent danger of losing their teeth. The sheer arithmetic of the situation -- a caseload of over 12,000 patients per periodontist -- speaks loudly for an alternative approach that professionals with less training can administer and supervise.

Fewer than half those 32 million are thought to be actually under treatment now and, according to current estimates, 90 million more Americans have gum disease in its earlier stages, which has also been shown to be responsive to the Keyes regimen.

With the need so great and surgery both painful and costly, a microscope in every dentist's office might well make baking soda, salt water and tetracycline a feasible and economical alternative, at least until the advent of a preventive vaccine that would solve the problem once and for all.

Even then, I'd find it hard to give up that baking soda-hydrogen peroxide paste. Since I've been using it my teeth have been whiter than they've been in years.